Anticorrosion unit



NGN. 1 l949 C, M, OSTERHELD 2,486,37

4 ANTICORROS IGN UNIT Filed May 28, 1945 /g-@l a ATTY Patented ov. 1949AN TIC ORROSION UNIT Clark M. Osterheld, Stoughton, Wis., assigner toMcGraw Electric Company, Elgin, Ill., a corporation of DelawareApplication May 28, 1945, Serial No. 596,241

9 Claims. l

My invention relates to corrosion preventing means and particularly tosuch means comprising a resistance element.

An object of my invention is to provide a corrosion preventing unit thatshall be usable in a variety of different applications and underdifferent conditions.

Another object of my invention is to provide a corrosion preventing unitthat shall be of use both in a metal hot water tank to prevent corrosionof the interior thereof as well as in the ground in preventing thecorrosion of iron pipes buried in the ground.

Other objects of my invention will either appear during a description ofseveral forms of device embodying my invention or will be pointed outduring the course of such description and set forth in the appendedclaims.

In the drawings,

Figure l is a vertical section through a hot water tank embodying thedevice embodying my invention,

Fig. 2 is a view in side elevation of the device,

Fig. 3 is a view, partly in elevation and partly in vertical,longitudinal section, corresponding to Fig. 2,

Fig. 4 is an assembly view of another use of the unit embodying myinvention, and

Fig. 5 is a view in partial section of a still further modification.

Referring rst of all to Fig. 1 of the drawings, I have there shown anordinary iron domestic hot water tank II having a lower cold water inletopening I3 and an upper hot water outlet opening I5. While I haveelected to show a standard domestic hot water tank ,my invention is notlimited solely to use in such hot water tanks and it is therefore to beunderstood that any water tank subject to corrosion may be substitutedtherefor.

I have shown an anti-corrosion unit I'I as having screw-threadedengagement with one of the walls of the tank II, in this case a sidewall and substantially intermediate the ends of the tank.

Referring now to Figs. 2 and 3 of the drawings, I have there illustratedthe anti-corrosion unit I 'I as comprising a metallic head I9 which maybe made of iron. Member I9 is provided with a square outer end ZI, andwith an intermediate screw-threaded portion 23, so that the unit may bescrewed into and out of a cooperating opening in a tank. Thescrew-threaded portion 23 may be of any suitable or desired diameter sothat it will i'lt into an opening in one of the walls of the tank II ina fluid-tight manner. The head I9 is hollow, having an opening 25 in itsinner end, which opening is adapted to receive an end portion of ametallic member 21 which is made of metal anodic relatively to the tankmetal, here iron. While I do not desire to be limited thereto, I havefound that making the member 2l of magnesium, gives very good resultsfor more than one reason.

The inner surface of recess or opening 25 is provided with a pair ofspaced annular grooves 29 for a purpose which will hereinafter appear.The outer surface of the reduced end portion of the anodic metallicmember 2'I is also provided with a pair of annular grooves 33 which arepreferably so positioned relatively to each other and relatively totheannular grooves 29 on the inner surface of the Walls surrounding theopenings 25, as to be aligned therewith.

The inner end portion of member 21 is provided with a recess 35 openingat the end thereof, in which I locate a resistor unit 31, the ends ofthe said resistor unit being connected to member 2l of the anodic metaland to the head I9 and par ticularly to the square end 2 I.

I may, in the course of assembly of the unit, position the member 2'I ofanodic metal in its proper operative position substantially as shown inFig. 3 of the drawings with the resistor unit 3'I being in the recess 35and with the terminals thereof electrically connected as describedhereinbefore after which I may pour in a lling 39 of an insoluble,non-absorptive phenolic condensation product, such as Bakelite. Afterpouring in the initially plastic, thermo-settable electric-im sulatingmaterial, the entire unit is then subjected to a baking operation inorder to cause solidication of the electric-insulating material whichwill tend to hold the member 21 in its fixed position relatively to thehead I9. The grooves 29 and 33 will tend to anchor the two members I9and SI in fixed positions relatively to each other, even l though theyare handled roughly during installation.

Referring now to Fig. 4 of the drawings, I have there illustrated aniron pipe 4I interred in the ground below the surface I3 thereof. It hasbeen found that buried iron pipe is subject to electrolytic actionbecause of the chemicals found in the soil. I provide an anti-corrosionunit I'I which is also buried below the surface of the ground and isconnected with the pipe 4I as by a conductor which is suitably soldered,brazed or welded to both the pipe 4I as well as to the head portion 2l.The interior construction will be the same as in Fig. 3.

Referring now to Fig. 5, I have there shown another modification adaptedto relatively large metal tank units. A hollow head 5I has a square end53 at its closed end and may have a screwthreaded portion 55 adjacentend 53 to permit of its being screwed into a large opening provided forthat purpose in a tank. A spacer 51 which may be made of porcelain, hasan outer diameter slightly less than the diameter of an opening 59 inhead 5 l. It has a central opening 6l therein and has an annulus 63 atits outer end, the inner periphery of which is adapted to engage withthe inner end of an anodic member 65 which is preferably made ofmagnesium.

A preformed resistor 61 is positioned within the central opening 6| andhas its respective terminals secured to two dished discs 69 and 1Ipositioned adjacent the respective ends of spacer 51. During theassembly of the unit the head 5I may be iixedly held with its recessedend uppermost, the spacer with the resistor and the two dished discselectrically connected thereto may then be dropped into the opening 59after which the member 65 may be placed in its proper operative positionin opening 59 and within the annulus 63. Then any suitable thermosetting electricinsulating material 13, such as filler 39 in Fig. 3, maybe applied while heated to cause it to flow and then allowed to cool,harden and set whereby the parts of the assembly will be held in iixedpositions relatively to each other. The degree of hardening should besuch that it may be driven into the ground as shown in Fig. 4, withoutdamage.

The conditions as regards the acidity of the water to which the membersI1 or 65 are subjected when applied or used in a tank Il as Well as whenthey are connected with an iron pipe 4i varies and since I desire toprovide anti-corrosion means in combination with an iron pipe or an irontank subject to Water of varying degrees of acidity, I may use resistors31 or 61 having an ohmic resistance which varies between, 4say 5 ohms to200 ohms although it is possible that a value on the order of 25 ohmsmay meet substantially all of the normal operating conditions. GenerallyI may say that I prefer to use a resistor v31 or 61, the ohmic value ofwhich is such that a current flow of one ampere per 3000 to 5000 Squarefeet of iron surface to be protected is obtained.

Extended tests on my part have shown that when an anti-corrosion unitsuch as unit I1 or 5| is used in a hot water tank, if the anodicmetallic metal element 21 or 65 is made of magnesium, there will be apotential difference of about 1.4 volts between the iron tank and theanodic member 21 or 65. Substantially the same `conditions may obtainwhen an anti-corrosion unit is buried in the soil and has its iron headconnected with an iron pipe. This potential diierence, particularly in ahot water tank, is sufficiently great so that no dissociation of theinner surface of the iron tank I l will occur even through the tankcontain slightly acidulous water. The voltage between the tank and theanodic member is high enough so that, irrespective of the position ofthe anti-corrosion unit in the tank, the potential difference betweenthe tank and the anodic element will be suliiciently high to insurecurrent owing from the anodic element to the iron of the tank at thepoint farthest away from the anodic element. A current will flow fromthe anodic element through the water and to the iron surface, the amountor value of such current being dependent upon the value Of the ohmicresistance of the resistor 31 or 61 which is designed or selected togive the above-mentioned current density. Thus by increasing theresistance of resistor 31 or 61, the amount of current iiowing throughthe resistor will be decreased and the rate of dissociation of theanodic member 21 or S5 will be reduced, that is the life of the anodicmember 21 or 65 Ywill be increased.

In all embodiments the solid plastic lling serves a dual purpose. Itholds the end portion of the metal anode member in the head and spacesthe end portion from direct electrical connection with the metal of thehead and permits electrical connection of the end portion of the headthrough the electrical resistor. When the embodiments of Figs. 2, 3 and5 are installed in a water tank the electric circuit between the anodemember and the tank is completed through the head, which makes metalliccontact with the tank Wall. The metal head in the embodiment of Fig. 4also constitutes a portion of the electrical circuit between the anodemember and the pipe to be protected. It will be noted that in allembodiments the necessity for securing bolts or other fasteningelements, likewise electrical terminal elements, is dispensed with.

Various modifications may be made in the device embodying my inventionwithout departing from the spirit or scope thereof and all suchmodifications clearly coming within the scope of the appended claims areto be considered as being part of my invention.

I claim as my invention:

l. An anti-corrosion unit comprising a tubular metal head closed at oneend, a metal anode member having an end portion extending into said headand spaced therefrom out of electrical contact, an electrical resistorin the head electrically connecting the head and the anode member, and asolid filling of plastic electric-insulating material in the headholding the head and anode member in fixed spaced relation to eachother.

2. An anti-corrosion unit comprising a tubular metal head closed at oneend, a metal anode member having an end portion extending into said headand spaced therefrom out of electrical contact, a solid iilling ofplastic electric-insulating material in the head holding the head andanode member in iixed spaced relation to each other, and an electricalresistor electrically interconnecting the head and the anode member andsealed in the head by the solid filling.

3. An anti-corrosion unit lcomprising a tubular metal head closed at oneend, a member of magnesium having an end portion Iitting into the headand spaced therefrom, a resistor having an ohmic resistance of between 5and 200 ohms in the head electrically connecting the head and the memberof magnesium and a lling of solid electric-insulating material in thehead covering entirely the resistor and holding all of said members infixed positions relatively to each other.

4. An anti-corrosion unit comprising a tubular iron head closed at oneend, a rod of magnesium having an end portion fitting into the head andspaced therefrom, a resistor having an ohmic resistance of between 10and 30 ohms in the head electrically connecting the head and the rod ofmagnesium, and a filling of solid electric-insulating material in thehead covering entirely the resistor and holding all of said members infixed positions relatively to each other.

5. An anti-corrosion unit for a hot water tank' comprising a tubulariron head closed at one end, an externally screw-threaded intermediateportion for water tight engagement with a hot water tank, annulargrooves in the inner surface of the head at the open end thereof, anelectrode of metal anodic to iron having an end portion extending intothe tubular head and out of engagement with the walls thereof and havingannular grooves in its outer surface, a resistor unit having aresistance of between 5 ohms and 200 ohms positioned in the recess ofsaid end portici*` of the electrode and having its ends electricallvconnected to the electrode and the head, and a filling of solidelectric-insulating material in the head filling the vacant spacetherein and holding all the parts in proper operative positionsrelatively to cach other.

6. An anti-corrosion u-nit for an iron hot water tank, comprising ahollow circular iron head closed at one end, an externallyscrew-threaded intermediate portion for water tight engagement with ahot water tank, spaced annular grooves in the inner surface of said headadjacent the open end thereof, a rod of magnesium having an end portionof reduced diameter with spaced annular grooves thereon extending intosaid hollow head out of engagement with the walls thereof and having arecess in its end portion, a resistor unit having an ohmic resistance ofbetween and 30 ohms positioned in said recess in said rod and having itsends connected to said head and to said rod and a filling of solidelectric-insulating material in the hollow iron head lling all thevacant space therein and holding all the parts of said unit in coaxialalinement with each other.

7. An anti-corrosion unit for an iron pipe buried in the ground,comprising a hollow iron head closed at one end and having spacedannular grooves therein adjacent the open end, an electrode of magnesiumhaving an end portion of reduced size with spaced annular grooves in itsouter surface extending into said hollow head out of engagement with thewalls thereof and having a recess in its end portion, a resistor unithaving an ohmic resistance of between 5 and 200 ohms in said recess inthe reduced portion of said electrode out of contact with the wallsthereof and a filling of solid electric-insulating material in saidhollow iron head filling all the vacant space therein and holding all ofsaid parts in proper operative positions relatively to each other whensaid unit is hammered into the ground.

8. An anti-corrosion unit comprising a tubular metal head closed at oneend, a spacer of solid electric-insulating material in said head at saidclosed end, said spacer having an opening therein and having an outerannular peripheral shoulder at that end thereof away from the closed endof said head, a magnesium member having one end in and spaced from saidtubular metal head and fitting within said peripheral annular shoulder,a resistor having an ohmic resistance of from 5 to 200 ohms located inthe opening in said spacer electrically connected to the metal head andto said magnesium member and a filling of solid electric-insulatingmaterial in the head and holding all of said members in fixed positionsrelatively to each other.

9. An anti-corrosion unit comprising a hollow metal head closed at oneend, a spacer of solid electric-insulating material in said hollow headat said closed end having a central opening therethrough, a magnesiumrod having one end portion in said hollow head, a resistor unit havingan ohmic resistance of from 10 to 30 ohms positioned in the centralopening in and spaced from said spacer, a pair of dished metal discs,one at each side of said spacer, having the terminals of said resistorunit connected thereto and a filling of solid electric-insulatingmaterial in the head filling all of the otherwise unoccupied space insaid head and holding said spacer and said magnesium rod in fixedpositions in said head.

CLARK M. OSTERI-IELD.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain 1873Germany June 12, 1936 Number Number

